Women in the United States exhibit very high levels of mobility among contraceptive methods. These high rates of movement mean that method switching is the primary determinant of the prevalence of specific contraceptive methods in the population and has direct implications for a woman's ability to avoid an unintended pregnancy. Despite its critical role in fertility regulation, however, there has been very little research directed at examining the determinants and consequences of the contraceptive switching process. The goal of the proposed study is to address these issues. Specifically, the proposed analysis will examine rates of movement among specific method types, including no method. It will determine the fluidity of the current method distribution. It will determine the implications of current switching rates for future utilization patterns. It will assess the impact on the contraceptive method switching process of the characteristics of women and the communities in which they live, and will investigate the relationship between the occurrence of important life events and method switching behavior. Finally, the study will provide the first systematic investigation of contraceptive switching among unmarried women. The study will be based on data from Cycle V of the National Survey of Family Growth. This data set affords the opportunity to obtain very current information about the contraceptive switching process. In using the data set to accomplish the goals of the proposed study, the analysis will provide the most accurate and most detailed information about contraceptive switching that has ever been available.